x = [-pi:0.05:-1.8, ...%这里的省略号是用来换行的
    -1.8:0.001:-1.2,...
    -1.2:0.05:1.2,...
    1.2:0.001:1.8,...
    1.8:0.05:pi];
y=sin(tan(x))-tan(sin(x));
plot(x,y)